1. Field of the Invention
The present invention relates generally to pressure thrust and more specifically to a system and method for drag reduction, which allows thrust output, fuel efficiency or both to be maximized.
2. Discussion of the Prior Art
The general concept of pressure thrust is known in the airfoil and aircraft design arts. The phenomenon uses energy of the air rushing past an airplane's wing, tail surfaces or fuselage, to push that wing, tail surface or fuselage forward. The energy required to force the free stream of airflow against the aircraft is less than the energy recovered from the airflow, allowing the system to generate a decrease in total energy required.
In the 1940s and 1950s the Griffith Aerofoil was developed. Researchers focused on very thick aerofoils, for use on span-loaded flying-wing transport and they proved a meaningful decrease in total power required for those designs. Fabio Goldschmied with help from Denis Bushnell at NASA uncovered and verified the pressure thrust phenomenon. The pressure thrust phenomenon is explained in Goldschmied, F. R., “Airfoil Static-Pressure Thrust: Flight-Test Verification,” AIAA Paper 90-3286, September 1990, the contents of which are hereby incorporated by reference in their entirety.
Additional documentation concerning the pressure thrust phenomenon can be found in Richards, E. J. and Burge, C. H. “An Airfoil Designed to Give Laminar Flow Over the Whole Surface with Boundary-Layer Suction,” A. R. C. RBM 2263, June 1943; Richards, E. J., Walker W. S. and Greening J. R., “Tests of a Griffith aerofoil in the 13 ft.times.9 ft. wind tunnel part 1, part 2, part 3, part 4, lift, drag, pitching moments and velocity distribution,” ARC/R&M-2148 ARC-7464 ARC-7561 ARC-8054 ARC-8055, 1944 and Richards, E. J., Walker, W. S. and Taylor, C. R., “Wind-Tunnel Tests on a 30% Suction Wing” A. R. C. RBM 2149, July 1945, Goldschmied, Fabio R., “Airfoil static-pressure thrust—Flight-test verification,” AIAA-1990-3286, AHS, and ASEE, Aircraft Design, Systems and Operations Conference, Dayton, Ohio, Sep. 17-19, 1990. 11 p., “Experimental investigation of a 40 percent thick half-span boundary layer control wing,” Witte, Gerhard R., and Sullivan, John P. (Purdue Univ., West Lafayette, Ind.), Merchant, Ali, and Drela, Mark (MIT, Cambridge, Mass.), AIAA-1998-407, Aerospace Sciences Meeting and Exhibit, 36th, Reno, Nev., Jan. 12-15, 1998, “Active control of separated flows on generic configurations at high Reynolds numbers,” Seifert A., and Pack, LaTunia G., (NASA, Langley Research Center, Hampton, Va.) AIAA-1999-3403, AIAA Fluid Dynamics Conference, 30th, Norfolk, Va., Jun. 28-Jul. 1, 1999, “Multiple Actuators Flow Control over a Glauert-Goldschmied type Airfoil at Low Reynolds Numbers,” Yom-Tov, J. and Seifert, A., Tel Aviv University, Tel Aviv, Israel, AIAA-2005-5389, 35th AIAA Fluid Dynamics Conference and Exhibit, Toronto, Ontario, Jun. 6-9, 2005, Kummer, J. D. Dang, T. Q., “High-Lift Propulsive Airfoil with Integrated Crossflow Fan,” JOURNAL OF AIRCRAFT 2006, VOL 43; NUMB 4, pages 1059-1068, Syracuse University, Syracuse, N.Y., GOLDSCHMIED, F. R. (SPERRY RAND CORP., SPERRY UTAH CO., ADVANCED SYSTEMS DEPT., SALT LAKE CITY, UTAH), “An approach to turbulent incompressible separation under adverse pressure gradients,” Journal of Aircraft 1965, 0021-8669 vol. 2 no. 2 (108-115), PARSONS, J. S. (Purdue Univ., Lafayette, Ind.); GOODSON, R. E. (Purdue Univ., Lafayette, Ind.); GOLDSCHMIED, F. R., “Shaping of axisymmetric bodies for minimum drag in incompressible flow,” Journal of Hydronautics 1974, 0022-1716 vol. 8 no. 3 (100-107), Goldschmied, Fabio R., “Aerodynamic Hull Design for HASPA LTA Optimization,” Journal of Aircraft 1978, 0021-8669 vol. 15 no. 9 (634-638), Goldschmied, F. R., Comment on “An Inverse Boundary-Layer Method for Compressible Laminar and Turbulent Boundary-Layers,” Journal of Aircraft 1977, 0021-8669 vol. 14 no. 5 (509-509), Goldschmied, F. R., “Integrated Hull Design, Boundary-Layer Control, and Propulsion of Submerged Bodies,” Journal of Hydronautics 1967, 0022-1716 vol. 1 no. 1 (2-11), and Goldschmied, F. R., “Flow Control of Centrifugal Jet-Flap Blowers for Air-Cushion Vehicles,” Journal of Hydronautics 1980, 0022-1716 vol. 14 no. 2 (48-55), the contents of which are hereby incorporated by reference in their entirety.
Further, U.S. Pat. No. 5,099,685 to McLean et al. discloses a “Boundary Layer Control Diffuser for a Wind Tunnel or the Like” and U.S. Pat. No. 5,358,200 to Onda discloses an “Airship,” which are hereby incorporated by reference in their entirety.
Accordingly, there is a clearly felt need in the art for a system and method for drag reduction, which allows thrust output, fuel efficiency or both to be maximized for suitable applications, such as vehicle body design.